The invention relates to a device for cooling and condensing fuel vapors for an internal combustion engine.
From EP 0 211 419 A2 a device of the aforementioned type is known which has a heat pipe whose evaporation zone is arranged in a chamber in a return line circulated by fuel, between the internal combustion engine and a fuel tank, which, however, can alternatively also be provided in the fuel tank or at the entrance of a pre-feed pump to cool the liquid fuel located there.
In internal combustion engines the fuel tank heats up when ambient temperatures rise. This leads to increased outgassing of more volatile hydrocarbons from the liquid fuel, which results in an increased gas pressure in the fuel tank. To avoid that the gas pressure reaches critical values, a tank ventilation valve is usually provided which opens when the gas pressure exceeds a predetermined threshold value. To avoid leaking of gaseous hydrocarbons (HC) into the environment, legislation requires an activated carbon filter to be provided between the tank ventilation valve and the environment. The activated carbon filter has the purpose to adsorb hydrocarbons contained in the gas mixture which leaks through the tank ventilation valve, so that only air can escape into the environment. To maintain the adsorption capacity of the activated carbon filter, the latter must be regularly regenerated by aspirating ambient air through the activated carbon filter into the intake tract of the internal combustion engine during operation of the internal combustion engine, to flush the activated carbon filter clear of hydrocarbons and to conduct the hydrocarbons together with the aspirated air into the combustion chambers of the internal combustion engine for combustion.
When a motor vehicle is exclusively driven by means of an internal combustion engine or as in the case of a hybrid vehicle alternately by an internal combustion engine and an electric motor, the activated carbon filter can be regenerated regularly, because the internal combustion engine is operated frequently. In contrast, electromotive operation predominates in so called plug-in motor vehicles with an electric motor which serves as driving engine, and an internal combustion engine which is carried along only as auxiliary motor and only serves for charging the vehicle batter. In these motor vehicles this can cause an activated carbon filter which is loaded with a greater amount of hydrocarbons not to be regenerated over an extended period of time. In turn, this can lead to bleed emissions, which means an undesired leaking of hydrocarbons from the activated carbon filter into the environment, as a result of diffusion processes. To avoid this, the activated carbon filter could be dimensioned larger which is, however, disadvantageous with regard to installation space and costs.